The invention relates to a leaf spring for holding down the brake-lining carriers of a disc brake wherein the brake-lining carrier has a friction-lining free section extending radially towards the outside onto which is fixed a holding section of the leaf spring, whereby the leaf spring has two shanks which are transversely angled from the holding section towards the brake-lining carrier and supported on two support surfaces, arranged at the bottom on both sides of an opening of a caliper unit, which opening accommodates the friction-lining free section of the brake-lining carrier.
In a leaf spring of this type, as described in German patent reference DE-OS 25 58 294, both shanks are identical in construction. When mounted, the leaf spring, supported against the caliper unit, exerts a centrally directed force on the brake-lining carrier. This means that the brake linings are only radially pretensioned against the respective guide surfaces which can be arranged either in the brake carrier or in the caliper unit. Disc brakes also have lateral guide surfaces against which the brake linings can support themselves during actuation of the brakes in dependence on the rotational direction of the brake disc. Thus, the occurring brake moment is transferred to and absorbed by a support member of the brake carrier.
In order to guarantee easy running of the brake linings in the guide section, both during the braking and the return after the brake release, a certain play is provided between the lateral surfaces of the brake-lining carrier and the lateral guide surfaces in the support member of the brake carrier, which play also serves to compensate manufacturing tolerances. However, this present play results in the brake-lining carrier, which is only radially pretensioned by the leaf spring, being dragged along during braking from its inoperative position in the direction of rotation of the brake disc due to the adhesive friction developing between the brake lining and the brake disc, and after having overcome the present play, abruptly abutting against the lateral guide surfaces of the brake carrier. This causes a most undesirable knocking sound in the brake, which is particularly disturbing during frequent braking in town traffic, or frequent braking at short intervals. Furthermore, such abrupt loading can cause damage to the brake-lining carrier and the support member of the brake carrier, thus no longer guaranteeing easy running of the brakelining carrier in the guide section.
A further disadvantage of the known leaf spring, which holds down the brake-lining carrier only in the radial direction, appears with a mounting position of the disc brake wherein the caliper unit is not above the brake disc but, as seen in the direction of travel, behind the vehicle axis. In this mounting position of the disc brake, the brake carriers will always be inclined, due to their own weight as well as vehicle vibrations, to abut against the lower lateral guide surface, so that not only the aforedescribed effect during braking is unavoidable, but additionally the knocking sounds when the brake is released.
Further springs for holding down of brake-lining carriers are described in German patent references DE-OS 2 558 141, DE-OS 3 323 362, DE-OS 3 621 507 and in European patent reference EP 0 248 385 A1. These already known holding-down springs exert only a pretensional force on the brake-lining carrier towards the center point of the brake disc.